JP2021110342A - Bearing ring of rolling bearing - Google Patents

Abstract

To provide a bearing ring of a rolling bearing, in which creep resistance of an anti-raceway surface can be improved.SOLUTION: A bearing ring of a rolling bearing is made of hardened steel, and comprises surfaces having an inner circumferential surface and an outer circumferential surface. One of the inner circumferential surface and the outer circumferential surface includes a raceway surface. The other of the inner circumferential surface and the outer circumferential surface provides an anti-raceway surface. A retained austenite amount in the steel of the anti-raceway surface is smaller than a retained austenite amount in the steel of the raceway surface. Difference between the retained austenite amount in the steel of the raceway surface and the retained austenite amount in the steel of the anti-raceway surface is 5 vol.% or more. Difference between a maximum value and a minimum value of the retained austenite amount in the steel of the anti-raceway surface measured along a circumferential direction of the bearing ring is 2 vol.% or less.SELECTED DRAWING: Figure 2

Description

The present invention relates to a raceway ring of a rolling bearing.

For example, Patent Document 1 (Japanese Unexamined Patent Publication No. 2017-187104) describes an inner ring of a rolling bearing. The inner ring of Patent Document 1 is made of hardened steel. The inner ring described in Patent Document 1 has an inner layer portion inside the inner ring and a surface layer portion surrounding the entire periphery of the inner layer. The surface layer portion exists not only on the outer peripheral surface side including the raceway surface but also on the inner peripheral surface side (anti-tracking surface side).

JP-A-2017-187104

As described above, in the inner ring described in Patent Document 1, since the surface layer portion exists not only on the outer peripheral surface side but also on the inner peripheral surface side, the inner diameter expands due to aging and the fit with the shaft becomes loose. , Creep may occur.

The present invention has been made in view of the above-mentioned problems of the prior art. More specifically, the present invention provides a raceway ring of a rolling bearing capable of improving creep resistance on an anti-raceway surface.

The raceway ring of the rolling bearing according to one aspect of the present invention is made of hardened steel and includes a surface having an inner peripheral surface and an outer peripheral surface. One of the inner peripheral surface and the outer peripheral surface includes a raceway surface. The other of the inner peripheral surface and the outer peripheral surface is an anti-orbital surface. The amount of retained austenite in the steel on the anti-track surface is smaller than the amount of retained austenite in the steel on the raceway surface. The difference between the amount of retained austenite in the steel on the raceway surface and the amount of retained austenite in the steel on the anti-track surface is 5% by volume or more. The difference between the maximum value and the minimum value of the amount of retained austenite in the steel on the anti-track surface measured along the circumferential direction of the raceway ring is 2% by volume or less.

In the raceway ring of the rolling bearing described above, a nitriding layer may be formed on the surface thereof. The difference between the amount of retained austenite in the steel on the raceway surface and the amount of retained austenite in the steel on the anti-track surface may be 10% by volume or more.

In the raceway ring of the rolling bearing, the hardness of the steel on the raceway surface may be 650 Hv or more. The difference between the maximum value and the minimum value of the hardness of the steel on the raceway surface measured along the circumferential direction of the raceway ring may be 20 Hv or less.

In the raceway ring of the rolling bearing, the hardness of the steel on the anti-tracking surface may be 600 Hv or more.

In the raceway ring of the rolling bearing, the amount of retained austenite in the steel may decrease with a gradient of 3% by volume / m or more and 300% by volume / m or less from the raceway surface to the anti-tracking surface.

In the raceway ring of the rolling bearing, the hardness of the steel may decrease with a gradient of ^{1 × 10 3} Hv / m or more and 100 × 10 ^{3 Hv / m or less from the raceway surface to the anti-track surface.}

In the raceway ring of the rolling bearing, the amount of retained austenite in the steel on the anti-tracking surface may be 5% by volume or less.

In the raceway ring of the rolling bearing, the average value of the residual austenite amount in the steel may be 10% by volume or less.

In the raceway ring of the rolling bearing described above, compressive residual stress may act on the raceway surface. In the raceway ring of the rolling bearing, the steel may be hypereutectoid steel.

In the raceway ring of the rolling bearing, the amount of carbon (C) in the steel may be 0.95% by weight or more and 1.1% by weight or less. The amount of silicon (Si) in the steel may be 0.3 weight percent or less. The amount of manganese (Mn) in the steel may be 0.5% by weight or less. The amount of chromium (Cr) in the steel may be 1.4% by weight or more and 1.6% by weight or less. In the raceway ring of the rolling bearing, the steel may be the high carbon chromium bearing steel SUJ2 defined in the JIS standard.

According to the raceway ring of the rolling bearing according to one aspect of the present invention, the creep resistance on the anti-tracking surface can be improved.

It is a top view of the inner ring 10. It is sectional drawing in II-II of FIG. It is sectional drawing of the inner ring 10 which concerns on a modification. It is a process drawing which shows the manufacturing method of the inner ring 10. It is a plane schematic diagram for demonstrating the 2nd tempering step S32. It is sectional drawing to explain the 2nd tempering step S32. It is a graph which shows the simulation result about the relationship between the heating time by a heating coil 30 and the temperature on the inner peripheral surface 20c and the outer peripheral surface 20d. It is a graph which shows the simulation result of the heating temperature of the outer peripheral surface 20d when the heating temperature of the inner peripheral surface 20c is changed. It is a graph which shows the influence of the heating temperature of the inner peripheral surface 20c on the difference between the maximum value and the minimum value of the retained austenite in the inner peripheral surface 20c measured along the circumferential direction of the member 20 to be processed. 6 is a graph showing the influence of the heating temperature of the inner peripheral surface 20c on the difference between the maximum value and the minimum value of the hardness of the inner peripheral surface 20c measured along the circumferential direction of the member 20 to be processed.

The details of the embodiment will be described with reference to the drawings. In the following drawings, the same or corresponding parts shall be designated by the same reference numerals, and duplicate explanations shall not be repeated.

(Structure of raceway ring of rolling bearing according to embodiment)
The configuration of the raceway ring of the rolling bearing according to the embodiment will be described below.

The raceway ring of the rolling bearing according to the embodiment is, for example, an inner ring of a deep groove ball bearing (hereinafter, referred to as “inner ring 10”). However, the raceway ring of the rolling bearing according to the embodiment is not limited to this. The raceway ring of the rolling bearing according to the embodiment may be an outer ring of a deep groove ball bearing, or may be a raceway ring of a rolling bearing other than the deep groove ball bearing.

The inner ring 10 is made of hardened steel. That is, this steel contains martensite crystal grains and retained austenite crystal grains. This steel may contain other than martensite crystal grains and retained austenite crystal grains (for example, ferrite crystal grains and carbide grains).

This steel may be, for example, hypereutectoid steel. The "hypereutectoid steel" is a steel containing carbon exceeding the eutectoid composition. The steels are, for example, 0.95 weight percent or more and 1.1 weight percent or more carbon (C), 0.3 weight percent or less silicon (Si), 0.5 weight percent or less manganese (Mn) and 1. It contains 4% by weight or more and 1.6% by weight or less of chromium (Cr). This steel is, for example, SUJ2, which is a high carbon chromium bearing steel defined in the JIS standard (JIS G 4805: 2008).

FIG. 1 is a plan view of the inner ring 10. FIG. 2 is a cross-sectional view taken along the line II-II of FIG. As shown in FIGS. 1 and 2, the inner ring 10 has an annular shape. The inner ring 10 has a central axis A.

The inner ring 10 has a first end surface 10a and a second end surface 10b, an inner peripheral surface 10c, and an outer peripheral surface 10d. The first end surface 10a, the second end surface 10b, the inner peripheral surface 10c, and the outer peripheral surface 10d may be collectively referred to as the surface of the inner ring 10.

The first end face 10a and the second end face 10b form end faces in a direction along the central axis A (hereinafter, referred to as "axial direction"). The second end surface 10b is the opposite surface of the first end surface 10a in the axial direction.

The inner peripheral surface 10c extends in a direction along the circumference centered on the central axis A (hereinafter, referred to as “circumferential direction”). The inner peripheral surface 10c faces the central axis A side. The inner peripheral surface 10c is connected to the first end surface 10a and the second end surface 10b. The inner ring 10 is fitted to a shaft (not shown) on the inner peripheral surface 10c.

The outer peripheral surface 10d extends in the circumferential direction. The outer peripheral surface 10d faces the side opposite to the central axis A. That is, the outer peripheral surface 10d is the opposite surface of the inner peripheral surface 10c in the direction orthogonal to the central axis A and passing through the central axis A (hereinafter, referred to as the “diameter direction”).

The outer peripheral surface 10d has a raceway surface 10da. The outer peripheral surface 10d is recessed on the inner peripheral surface 10c side in the raceway surface 10da. The raceway surface 10da has an arc shape in a cross-sectional view passing through the central axis A. The raceway surface 10da is a surface that comes into contact with a rolling element (not shown). The anti-orbital plane is a plane on the opposite side of the orbital plane 10da in the radial direction. In the inner ring 10, the inner peripheral surface 10c is an anti-orbital plane.

The amount of retained austenite on the inner peripheral surface 10c, which is the anti-orbital plane, is smaller than the amount of retained austenite on the raceway surface 10da. The average value of the amount of retained austenite in the steel constituting the inner ring 10 is preferably 10% by volume or less. The "average value of the amount of retained austenite in the steel constituting the inner ring 10" is a plurality of points arranged at equal intervals between the raceway surface 10da and the inner peripheral surface 10c along the radial direction of the inner ring 10. It is a value obtained by integrating the distribution curve of the retained austenite amount obtained by the measurement in the circumferential direction and dividing it by the cross-sectional area of the raceway ring (inner ring 10) parallel to the circumferential direction. The number of measurement points is, for example, 5 or more.

The difference between the maximum value and the minimum value of the retained austenite amount on the inner peripheral surface 10c measured along the circumferential direction of the inner ring 10 is preferably 2% by volume or less. The difference between the maximum value and the minimum value of the retained austenite amount on the raceway surface 10da measured along the circumferential direction of the inner ring 10 is preferably 2% by volume or less.

The difference between the amount of retained austenite on the inner peripheral surface 10c and the amount of retained austenite on the raceway surface 10da is 5% by volume or more. The amount of retained austenite on the inner peripheral surface 10c is preferably 5% by volume or less.

The amount of retained austenite in the steel constituting the inner ring 10 decreases from the raceway surface 10da to the inner peripheral surface 10c. The gradient of this decrease is preferably 3% by volume / m or more and 300% by volume / m or less. The gradient of this decrease may be 0.5% by volume or more and 10% by volume or less. The gradient of this decrease is calculated by dividing the difference between the amount of retained austenite on the raceway surface 10da and the amount of retained austenite on the inner peripheral surface 10c by the distance between the raceway surface 10da and the inner peripheral surface 10c.

The amount of retained austenite in the steel constituting the inner ring 10 is measured by an X-ray diffraction method. More specifically, the amount of retained austenite is obtained by comparing the intensities of the diffraction peaks of each phase obtained by irradiating with X-rays.

It is preferable that a compressive residual stress acts on the raceway surface 10da. The minimum value of compressive residual stress on the raceway surface 10 da is preferably 100 MPa or more. The residual stress on the orbital plane 10 da is measured by the X-ray diffraction method. More specifically, the residual stress on the orbital plane 10da is measured based on the change in the diffraction peak angle when the orbital plane 10da is irradiated with X-rays.

The hardness on the raceway surface 10da is higher than the hardness on the inner peripheral surface 10c. The hardness of the raceway surface 10 da is preferably 650 Hv or more. The hardness of the inner peripheral surface 10c is preferably 600 Hv or more.

The hardness of the steel constituting the inner ring 10 decreases from the raceway surface 10da to the inner peripheral surface 10c. The gradient of this decrease ^{is preferably 1 × 10 3} Hv / m or more and 100 × 10 ³ Hv / m or less. The gradient of this decrease is calculated by dividing the difference between the hardness on the raceway surface 10da and the hardness on the inner peripheral surface 10c by the distance between the raceway surface 10da and the inner peripheral surface 10c. The difference between the maximum value and the minimum value of the hardness of the inner peripheral surface 10c measured along the circumferential direction of the inner ring 10 is preferably 20 Hv or less. The difference between the maximum value and the minimum value of the hardness on the raceway surface 10da measured along the circumferential direction of the inner ring 10 is preferably 20 Hv or less.

The hardness of the raceway surface 10da and the hardness of the inner peripheral surface 10c are measured according to the Vickers hardness test method defined in the JIS standard (JIS Z 2244: 2009).

<Modification example>
FIG. 3 is a cross-sectional view of the inner ring 10 according to the modified example. As shown in FIG. 3, a nitrification layer 10e may be formed on the surface of the inner ring 10. The nitrogen concentration in the steel located in the immersion layer 10e is higher than the nitrogen concentration in the steel located in the steel other than the immersion layer 10e. The nitrogen concentration in the steel located in the immersion layer 10e is, for example, 0.1% by weight or more. The nitrogen concentration in the steel located in the immersion layer 10e may be 0.4% by weight or more. The nitrogen concentration in steel is measured by EPMA (Electron Probe Micro Analyzer).

When the nitriding layer 10e is formed on the surface of the inner ring 10, the difference between the amount of retained austenite on the inner peripheral surface 10c and the amount of retained austenite on the raceway surface 10da is, for example, 10% by volume or more.

(Method of manufacturing a raceway ring of a rolling bearing according to an embodiment)
The method of manufacturing the inner ring 10 will be described below.

FIG. 4 is a process diagram showing a method for manufacturing the inner ring 10. As shown in FIG. 4, the method for manufacturing the inner ring 10 includes a preparation step S1, a quenching step S2, a tempering step S3, and a post-treatment step S4. In the preparation step S1, the annular work target member 20 to be the inner ring 10 is prepared by going through the quenching step S2, the tempering step S3, and the post-treatment step S4.

When the nitriding layer 10e is formed on the surface of the inner ring 10, the surface of the member 20 to be processed is subjected to a nitriding treatment prior to the quenching step S2. The immersion treatment is performed by holding the member 20 to be processed at a predetermined temperature for a predetermined time in, for example, an atmospheric gas containing nitrogen (for example, ammonia (NH _{3) gas).}

In the quenching step S2, the member 20 to be processed is quenched. The quenching step S2 includes a heating step S21 and a cooling step S22. In the heating step S21, the member 20 to be processed _{is heated to a temperature of A 1} point or higher and held for a predetermined time. A ₁ point is the temperature at which ferrite in steel begins to transform into austenite. By performing the heating step S21, austenite crystal grains are generated in the steel constituting the member 20 to be processed.

The cooling step S22 is performed after the heating step S21. In the cooling step S22, the member 20 to be processed is cooled to a temperature equal to or lower than the Ms point. The Ms point is the temperature at which the transformation from austenite to martensite begins. Therefore, in the cooling step S22, some of the austenite crystal grains in the steel constituting the processing target member 20 become martensite crystal grains.

The tempering step S3 is performed after the quenching step S2. In the tempering step S3, the member 20 to be processed is tempered. The tempering step S3 includes a first tempering step S31 and a second tempering step S32. The second tempering step S32 is performed after the first tempering step S31.

In the first tempering step S31, a tempering process is performed on the entire member 20 to be processed. In the first tempering step S31, processing target member 20 is held in the heating to a temperature lower than the A ₁ transformation point. More specifically, the first tempering step S31 is performed, for example, by holding the member 20 to be processed at a temperature of 180 ° C. or higher and 230 ° C. or lower.

FIG. 5 is a schematic plan view for explaining the second tempering step S32. FIG. 6 is a schematic cross-sectional view for explaining the second tempering step S32. As shown in FIGS. 5 and 6, the heating in the second tempering step S32 is performed by, for example, induction heating.

More specifically, the heating coil 30 is arranged at a position facing the inner peripheral surface 20c of the member 20 to be processed, and induces and heats the inner peripheral surface 20c. The processing target member 20 is rotated around the central axis. The rotation speed of the member 20 to be processed is, for example, 100 rotations / minute or more and 200 rotations / minute or less. When the inner peripheral surface 20c is heated by the heating coil 30, the outer peripheral surface 20d of the member 20 to be processed is cooled by a cooling jacket (not shown). A cooling liquid such as water is flowed through the cooling jacket. The flow rate of the coolant is, for example, 5 L / min or more and 40 L / min or less.

FIG. 7 is a graph showing the simulation results regarding the relationship between the heating time by the heating coil 30 and the temperatures on the inner peripheral surface 20c and the outer peripheral surface 20d. In FIG. 7, the horizontal axis is the heating time (unit: seconds) by the heating coil 30, and the vertical axis is the temperature (unit: ° C.) on the inner peripheral surface 20c and the outer peripheral surface 20d. The simulation of FIG. 7 was performed under the conditions that the heating temperature of the inner peripheral surface 20c was 420 ° C., the outer peripheral surface 20d was water-cooled, and the distance between the inner peripheral surface 20c and the outer peripheral surface 20d was 3 mm. As shown in FIG. 7, in the tempering step S3, the heating temperature of the outer peripheral surface 20d is lower than the heating temperature of the inner peripheral surface 20c.

FIG. 8 is a graph showing a simulation result of the heating temperature of the outer peripheral surface 20d when the heating temperature of the inner peripheral surface 20c is changed. In FIG. 8, the horizontal axis represents the heating temperature (unit: ° C.) of the inner peripheral surface 20c, and the vertical axis represents the heating temperature (unit: ° C.) of the outer peripheral surface 20d. The simulation of FIG. 8 was performed under the same conditions as the simulation of FIG. 7 except that the heating temperature of the inner peripheral surface 20c was changed. As shown in FIG. 8, the heating temperature of the outer peripheral surface 20d is a linear expression of the heating temperature of the inner peripheral surface 20c. Assuming that the heating temperature of the inner peripheral surface 20c is x and the heating temperature of the outer peripheral surface 20d is y, y = a × x + b (a is a positive number less than 1 and b is a positive number). Is called "Equation 1").

The heating temperature of the inner peripheral surface 20c and the outer peripheral surface 20d is a temperature lower than the _{A 1} transformation point. The heating temperature of the inner peripheral surface 20c is, for example, 250 ° C. or higher. The heating temperature of the outer peripheral surface 20d is, for example, 150 ° C. or lower.

For example, as described in Japanese Patent Application Laid-Open No. 10-102137, the volume ratio (M ₁ ) of the retained austenite in the steel constituting the work target member 20 after the second tempering step S32 is performed is No. _{2 Using the volume ratio (M 0} ), heating temperature (T), and heating time (t) of retained austenite in the steel constituting the member 20 to be processed before the tempering step S32 is performed _{, M 1} = M _0. × {A × exp (−Q / RT) × t ⁿ } (A, Q and n are constants, R is a gas constant) (hereinafter, this equation is referred to as “Equation 2”).

Therefore, by appropriately adjusting the heating temperature and heating time of the inner peripheral surface 20c by the heating coil 30, the heating temperature of the outer peripheral surface 20d can be appropriately adjusted, and accordingly, the volume ratio of the retained austenite in the inner peripheral surface 20c. And the volume ratio of retained austenite on the outer peripheral surface 20d can be adjusted as appropriate.

For example, as described in References (Takeshi Inoue, "New Tempering Parameters and Application to Tempering Integration Method Along Its Continuous Temperature Curve", Iron and Steel, 66, 10 (1980), 1533). The hardness (Hv) of the steel constituting the work target member 20 after the tempering step S3 is determined by using the heating time (t) and the heating temperature (T) as Hv = c × log + d / T + e ( c, d, and e are constants) (hereinafter, this equation is referred to as "Equation 3"). Therefore, the hardness of the inner peripheral surface 20c can be appropriately adjusted by appropriately adjusting the heating temperature and the heating time of the inner peripheral surface 20c by the heating coil 30.

The heating in the second tempering step S32 is performed so that the difference between the maximum value and the minimum value of the heating temperature on the inner peripheral surface 20c measured along the circumferential direction of the member 20 to be processed is 20 ° C. or less. The difference between the maximum value and the minimum value of the heating temperature on the inner peripheral surface 20c measured along the circumferential direction of the processing target member 20 can be adjusted by, for example, the rotation speed of the processing target member 20.

FIG. 9 is a graph showing the effect of the heating temperature of the inner peripheral surface 20c on the difference between the maximum value and the minimum value of the retained austenite on the inner peripheral surface 20c measured along the circumferential direction of the member 20 to be processed. In FIG. 9, the horizontal axis is the heating temperature (unit: ° C.) of the inner peripheral surface 20c, and the vertical axis is the maximum value of the residual austenite amount on the inner peripheral surface 20c measured along the circumferential direction of the member 20 to be processed. The difference between the minimum value and the minimum value (unit: volume percent). In FIG. 9, ΔT indicates the difference between the maximum value and the minimum value of the heating temperature on the inner peripheral surface 20c measured along the circumferential direction of the member 20 to be processed. The graph of FIG. 9 is created using the above equations 1 and 2.

As shown in FIG. 9, the smaller the difference between the maximum value and the minimum value of the heating temperature on the inner peripheral surface 20c measured along the circumferential direction of the work target member 20, the smaller the difference between the maximum value and the minimum value, the more along the circumferential direction of the work target member 20. The difference between the maximum value and the minimum value of the retained austenite amount on the inner peripheral surface 20c measured in the above is small. More specifically, when the difference between the maximum value and the minimum value of the heating temperature on the inner peripheral surface 20c measured along the circumferential direction of the member 20 to be processed is 20 ° C., the inner peripheral surface 20c is heated. By appropriately adjusting the temperature, the difference between the maximum value and the minimum value of the residual austenite amount on the inner peripheral surface 20c measured along the circumferential direction of the member 20 to be processed can be set to 2% by volume or less.

FIG. 10 is a graph showing the effect of the heating temperature of the inner peripheral surface 20c on the difference between the maximum value and the minimum value of the hardness of the inner peripheral surface 20c measured along the circumferential direction of the member 20 to be processed. In FIG. 10, the horizontal axis is the heating temperature (unit: ° C.) of the inner peripheral surface 20c, and the vertical axis is the maximum value of the hardness of the inner peripheral surface 20c measured along the circumferential direction of the member 20 to be processed. The difference from the minimum value (unit: Hv). In FIG. 10, ΔT indicates the difference between the maximum value and the minimum value of the heating temperature on the inner peripheral surface 20c measured along the circumferential direction of the member 20 to be processed. The graph of FIG. 10 is created by using the above equations 1 and 3.

As shown in FIG. 10, the smaller the difference between the maximum value and the minimum value of the heating temperature on the inner peripheral surface 20c measured along the circumferential direction of the work target member 20, the smaller the vertical axis is the circumference of the work target member 20. The difference between the maximum value and the minimum value of the hardness on the inner peripheral surface 20c measured along the direction is small. More specifically, when the difference between the maximum value and the minimum value of the heating temperature on the inner peripheral surface 20c measured along the circumferential direction of the work target member 20 is 20 ° C., the circumference of the work target member 20 The difference between the maximum value and the minimum value of the hardness on the inner peripheral surface 20c measured along the direction can be 20 Hv or less.

Table 1 shows the residual stress on the outer peripheral surface 20d before and after the second tempering step S32 is performed. In the example of Table 1, the heating temperature of the inner peripheral surface 20c was set to 300 ° C. The steel constituting the member to be processed was designated as SUJ2. As shown in Table 1, before the second tempering step S32 was performed, the tensile residual stress acted on the outer peripheral surface 20d. On the other hand, after the second tempering step S32 was performed, the compressive residual stress acted on the outer peripheral surface 20d. More specifically, the compressive residual stress was 100 MPa or more at a position where the distance from the outer peripheral surface 20d was up to 0.2 mm.

In the tempering step S3, since the first tempering step S31 is performed before the second tempering step S32 is performed, the second tempering step S32 can be completed in a relatively short time, and the tempering can be completed. The productivity of step S3 can be improved.

In the post-treatment step S4, post-treatment is performed on the member 20 to be processed. This post-treatment includes grinding of the processing target member 20, cleaning of the processing target member 20, and the like. With the above, the manufacturing process of the inner ring 10 is completed.

(Effect of rolling bearing according to the embodiment)
The effect of the inner ring 10 will be described below.

In the inner ring 10, the amount of retained austenite on the anti-orbital plane (inner peripheral surface 10c) is 5% by volume or more less than the amount of retained austenite on the raceway surface 10da. The dimensional change of the inner peripheral surface 10c is small. Therefore, according to the inner ring 10, the creep resistance on the anti-track surface can be improved. By setting the amount of retained austenite on the inner peripheral surface 10c to 5% by volume or less (10% by volume or less when the nitriding layer 10e is formed), the creep resistance on the anti-orbital surface can be further improved. can.

In the inner ring 10, the amount of retained austenite on the inner peripheral surface 10c is smaller than the amount of retained austenite on the raceway surface 10da (from another viewpoint, the amount of decrease in retained austenite on the inner peripheral surface 10c is the amount of retained austenite on the raceway surface 10da. The shrinkage on the inner peripheral surface 10c side after the end of the second tempering step S32 is larger than that on the raceway surface 10da side.

Due to this difference in the amount of shrinkage, compressive residual stress acts on the raceway surface 10da. In the inner ring 10, the difference between the amount of retained austenite on the inner peripheral surface 10c and the amount of retained austenite on the raceway surface 10da is 5% by volume or more (10% by volume or more when the nitriding layer 10e is formed on the surface). Therefore, a large (for example, 100 MPa or more) compressive residual stress acts on the raceway surface 10 da. Therefore, according to the inner ring 10, the rolling fatigue characteristic on the raceway surface 10da can be improved.

In the inner ring 10, the difference between the maximum value and the minimum value of the retained austenite amount on the inner peripheral surface 10c (orbital plane 10da) measured along the circumferential direction of the inner ring 10 is 2% by volume or less, and the inner ring 10 Since the difference between the maximum value and the minimum value of the hardness on the inner peripheral surface 10c (orbital plane 10da) measured along the circumferential direction is 20 Hv or less, the inner ring 10 is uniform along the circumferential direction. It will have characteristics.

Although the embodiment of the present invention has been described above, it is possible to modify the above-described embodiment in various ways. Moreover, the scope of the present invention is not limited to the above-described embodiment. The scope of the present invention is indicated by the scope of claims and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

The above embodiments are particularly advantageously applied to the raceway rings of rolling bearings.

10 Inner ring, 10a 1st end surface, 10b 2nd end surface, 10c inner peripheral surface, 10d outer peripheral surface, 10da track surface, 10e quenching layer, 20 members to be processed, 20c inner peripheral surface, 20d outer peripheral surface, 30 heating coil, A Central axis, S1 preparation process, S2 quenching process, S3 tempering process, S4 post-processing process, S21 heating process, S22 cooling process, S31 first tempering process, S32 second tempering process.

Claims (12)

The raceway ring of a rolling bearing
The raceway ring is made of hardened steel and has a surface having an inner peripheral surface and an outer peripheral surface.
One of the inner peripheral surface and the outer peripheral surface includes a raceway surface.
The other of the inner peripheral surface and the outer peripheral surface is an anti-orbital plane.
The amount of retained austenite in the steel on the anti-track surface is smaller than the amount of retained austenite in the steel on the raceway surface.
The difference between the amount of retained austenite in the steel on the raceway surface and the amount of retained austenite in the steel on the anti-track surface is 5% by volume or more.
A rolling bearing raceway ring in which the difference between the maximum value and the minimum value of the residual austenite amount in the steel on the anti-tracking surface measured along the circumferential direction of the raceway ring is 2% by volume or less. An immersion layer is formed on the surface.
The raceway ring of a rolling bearing according to claim 1, wherein the difference between the amount of retained austenite in the steel on the raceway surface and the amount of retained austenite in the steel on the anti-tracking surface is 10% by volume or more. The hardness of the steel on the raceway surface is 650 Hv or more, and the hardness is 650 Hv or more.
The track of the rolling bearing according to claim 1 or 2, wherein the difference between the maximum value and the minimum value of the hardness of the steel on the raceway surface measured along the circumferential direction of the raceway ring is 20 Hv or less. ring. The raceway ring of a rolling bearing according to any one of claims 1 to 3, wherein the hardness of the steel on the anti-track surface is 600 Hv or more. The amount of retained austenite in the steel decreases with a gradient of 3% by volume / m or more and 300% by volume / m or less from the raceway surface to the anti-tracking surface, any one of claims 1 to 4. The raceway ring of the rolling bearing described in. Any one of claims 1 to 5, wherein the hardness of the steel decreases from the raceway surface to the anti-tracking surface with ^{a gradient of 1 × 10 3} Hv / m or more and 100 × 10 ^{3 Hv / m or less.} The raceway ring of the rolling bearing according to item 1. The raceway ring of a rolling bearing according to any one of claims 1 to 6, wherein the amount of retained austenite in the steel on the anti-track surface is 5% by volume or less. The raceway ring of a rolling bearing according to any one of claims 1 to 7, wherein the average value of the amount of retained austenite in the steel is 10% by volume or less. The raceway ring of a rolling bearing according to any one of claims 1 to 8, wherein compressive residual stress acts on the raceway surface. The raceway ring of a rolling bearing according to any one of claims 1 to 9, wherein the steel is a hypereutectoid steel. The carbon content in the steel is 0.95% by weight or more and 1.1% by weight or less.
The amount of silicon in the steel is 0.3 weight percent or less.
The amount of manganese in the steel is 0.5% by weight or less.
The raceway ring of a rolling bearing according to any one of claims 1 to 10, wherein the amount of chromium in the steel is 1.4% by weight or more and 1.6% by weight or less. The raceway ring of a rolling bearing according to any one of claims 1 to 11, wherein the steel is a high carbon chrome bearing steel SUJ2 defined in JIS standards.

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